Measurement of Casing Buckling in Producing Intervals

As part of a program to ascertain damage configuration in some South Louisiana wells, a gyroscopic tool was designed for measuring lateral casing deflection over short intervals. Use of this tool has revealed that the principal mode of damage is not collapse or shear, as previously supposed, but buckling in the producing interval. Introduction During 1966 a study of casing damage was conducted in the South Pass Block 24 and Block 27 fields, located in the delta of the Mississippi River. The study was started because of the rising workover costs associated with a rapid increase in casing damage - from three instances discovered in 1963 to 23 in 1965. Since 1965, casing damage discoveries have continued at a rate of 30 or more per year. As a result of the damage, primarily in the production interval, workovers have become more expensive because of extensive fishing and repair operations; wells have had to be replaced because of forced abandonments; and some oil reserves have been lost. Attempts had been made before the 1966 study to ascertain the shape of the damage through use of lead impression blocks and analysis of work string assemblies run past the damaged interval. From these observations damage was interpreted as collapse, shear or buckling. Occasionally a window would inadvertently be cut and a rathole drilled alongside the casing close to the producing interval. Although we now know that this resulted from the inability of relatively stiff hookups to follow the "kink", at that time we thought it was because of lateral shear or collapse. The initial study revealed that there was inadequate information about casing damage configuration and that lack of adequate knowledge was leading to confusion about the cause of the failures and proper corrective measures. Following a survey of the industry, which revealed that there were no suitable measuring instruments available, Sperry-Sun Well Surveying Co. was requested to devise a tool, now called the Kinkmeter, capable of measuring lateral casing deflection. Specifications were set on the severity of deflection the tool would be capable of passing through while recording bearing and inclination at stations 1 ft apart. At the same time a 7-in. casing caliper tool was developed through modification of an existing Kinley Caliper Co. tool. In the meantime, the Lynes and Halliburton impression packers and the Lavall down-hole stereo camera were run. Because of the nature of the damage, the difficulty of positioning the tools properly, and the flooding of the Lavall camera following the failure of a fitting, little diagnostic information was obtained about the casing. The Sperry-Sun Kinkmeter was developed, tested in casing deflected to prescribed conditions and placed in use in the field during 1966. This report presents the results of use of the tool since it was first made available. The Kinley caliper tool has passed acceptance tests and is now also used in the field. Information obtained to date with the caliper tool has supported the concept that the principal mode of casing damage has been buckling. The information provided by the new measurement tools has been important in understanding the casing damage problem in the Gulf Coast region. JPT P. 255